Master cylinder having a booster in combination therewith



April 6, 1954 A. M. KIRK 2,674,097

MASTER CYLINDER HAVING A BOOSTER IN COMBINATION THEREWITH Filed July 27, 1950 2 Sheets-Sheet l n ,I 6'# (5:3 ATTI: R N EYs A. M. KIRK April 6, 1954 MASTR CYLINDER HAVING A BOOSTER IN COMBINATION THEREWITH 2 Sheets-Sheet 2 Filed Jul'y 27, 1950 Bf mzm Ill! ATTORNEYS Patented Apr. 6, 1954 Y' UNITED STATES PATENT OFFICE MASTER CYLINDER HAVING A BOOSTER IN COMBINATION THEREWITH Application July 27, 1950, Serial No. 176,204

(Cl. Gil-1546) 2 Claims. l

This invention relates to brake systems of motor vehicles and particularly master cylinders of brake systems, and in particular this invention relates to a master cylinder having a booster in combination therewith wherein bralfzes are actuated, lirst by brake fluid from a low pressure area in the cylinder and booster and with a slight continued forward movement of the brake pedal high pressure fluid is provided in the booster and 4directly applied to the brakes.

The purpose of this invention is to improve the operation of master cylinders of brake systems whereby duid pressure applied to brakes of a vehicle is built up gradually and smoothly whereby the pressure of the braises is evenly and at the same time positively applied,

In the conventional master cylinder a ioot pedal drives the duid into the brake system by means of s piston in cylinder and excessive pressure is returned to the storage compartment of the master cylinder through a by-pass. With the elements directly connected scale developing from rust and corrosion Works small rubber cupshaped discs and packing rings and leaks result therefrom. Master cylinders of the conventional type also use sealing rings only at the ends of the plunger .or piston and when the end ring is darn--v aged the pressure of the brake fluid is lost. With this thought in mind this invention contemplates a master cylinder having a housing with a removable cylinder threaded in hubs therein, With a foot pedal actuated piston slidably .mounted .in the cylinder and with a booster cylinder having a high pressure piston therein .extended from one side of the housing and` having a connection exl,

tended therefrom to the brake system ofa vehicle in Which the device is installed.

The object of this invention is, therefore, .to provide means for constructing a combination master cylinder vand booster whereby low and high pressure` areas are obtained by pistons in aligned cylinders and whereby high pressure is created with ya continued movement of the foot or .brake lever.

Another object of the invention is to Aprovide a combination master cylinder and booster wherein the parts are arranged to eliminate damage caused by scale, corrosion, and the like.

Another object of the invention is to provide a combination master cylinder and booster that may be installed in brake systems and fluid pressure actuated devices now in use.

A further object .of the invention is to provide o combination master cylinder and booster lor `lor-also and .other fluid pressure systems which is of a comparatively simple aud economical conf struction.

With these and other coiccts und odvoh'cogoc view the invention embodies c master cylinder housing having o cylindrical casing extended therefrom with a cylinder removably mounted ih the housing, another cylinder removably mounted iu the extended casing and with pistons ,and suit-vy able packing and resilient clcmcuts provided niu the cylinders whereby low pressureorcos are :first created, and, with continued movement of a brake pedal. a high pressure croc is provided iu the outlet end of the booster.

Other features and advantages ol thc invention will appear from the following description tagen in connection with the drawings wherein:

Figure 1 is a longitudinal section through thc combination muster cylinder und booster Showihg the parts in the free positions,

Figure 2 is a similar View illustrating the positions of the parts with the piston of the master cylinder actuated by e foot pedal oud with thc high pressure pistou also actuated to provlolc fluid under high pressure lh the outlet cud of thc booster.

Figure 3 is a .cross section through thc loopster taken on line .3-3 o f Figure l Showing the po tions of the openings bctwocol .tho loW and high pressure arcas of Athe device.

Figure 4 is an yend elevational view of the master cylinder housug looking toward tho cpd thereof where pressure is ,applied from a .foot lever.

Figure 5 is a cross .Sectionv through the housing taken on line 55-5 o f Figure l.

Figure 6 is a detail .showing a perforated disc in the end of the piston of the master cylinder.

Figure 'l is a cross section .through thc disc taken on line 'i-l of Figure 6.

Figure 8 is a detail 4Showing a Washer v providing a check valve inV .the cud of thc. pistou Yof tho master cylinder. with the parts .Shcwh op on# larged scale.

Figure 9 is a cross sectioh through the washer taken. on line 9h19 of Figure 8.

Figure l0 is a detail showing the cap posi-tiche@ over thc outlet opening which extends. through o out ou the outer cod of the booster cylinder with the parts shown on an enlarged scale.

lFigure ,11 ls ,a cross section through tho cop the return movement of tho vpistou of' lll-lcY master cylinder whereby the pressure unseats the washer, shown in Figure 9 in order to break the vacuum whereby the piston returns with a free movement.

Referring now to the drawings wherein like reference characters denote corresponding parts the combination master cylinder and booster of this invention includes a cylinder I9 in a housing Il with a piston I2 in the cylinder, and a booster cylinder I3 having a piston I4 therein and positioned in the outer part of an extended cylindrical casing I5 which is integral with and extends from the master cylinder housing.

The cylinder I0 is formed as illustrated in Figures l and 2 with threaded sections I6 and I1 that are threaded into hubs I8 and I9, respectively, of the housing II and the cylinder is provided with annular flanges and 2| that seat against the ends of the hubs to seal the ends of the threads. The outer end of the cylinder is provided with a bead 22 having a plate 23 secured in a recess` 24 therein by a spring ring 25 that snaps into an annular recess 23. The plate 23 is provided with an opening 21 through which a rod 28 extended from a brake lever extends. The rod extends into an opening 29 in the end of the piston I2 and packing rings 39 and 3l are positioned in annular recesses 32 and 33 in the piston.

The piston is provided with a flange 34 that abuts the plate 23 and also a iiange 35 that is positioned between the packing Washers and 3 I.

Similar cup-shaped packing washers 33 and 31 are mounted on the opposite end of the piston and these washers are held against annular ribs or flanges 38 and 39, respectively.

The inner end of the piston is provided with a bore 40 having a perforated disc `4I positioned against a shoulder 42 therein and a check washer 43 with a pin 44 extended from the outer surface thereof is resiliently held against the inner end of the piston by a spring 45 positioned between the check washer and perforated disc.

The check washer 43 is positioned over the end of a passage 4E extended from the center of the piston to an annular recess 41 which provides communicating means with the interior of the master cylinder housing il and the interior of the cylinder I9 through a port 48. A similar port, the size of which is less than that of the port 48 is provided through the wall of the cylinder I9 as indicated by the numeral 49 and this port provides communicating means between the interior of the housing II and the inside of the cylinder I0 whereby brake iiuid of the housing II lls the low pressure area in the outer end of the cylinder I0 and interior of the cylindrical casing I5.

A spring 50 holds the piston I2 in the position shown in Figure l until the piston is moved by the rod 28 of the foot lever.

The perforated disc 4I is provided with an internally threaded hub 5I which provides a seat for one end of the spring 45 with the opposite end positioned over the pin 44 oi the check washer 43.

The booster cylinder I3Y is provided with a threaded boss 52 by which it is threaded in the outer end of the cylinder casing I5 and a packing washer 53 is provided between the end of the casing I5 and a hub 54 on the outer end or the cylinder. A nut 55 is threaded in the outer end of the cylinder with a gasket 56 between the end of the nut and end of the cylinder and a tube 51 threaded into an opening 53 in the outer end of the nut extends to the brake system of the vehicle and provides means for carrying the brake fluid to the brakes of the system. The inner end 4 of the nut 55 is provided with a boss 59 having an annular recess 60 and a gasket 6I, positioned in the recess provides sealing means between the end of the cylinder I3 and inner end of the nut 55. As illustrated in detail in Figure 11 a perforated .cap 62 with a resilient washer 63 secured against the inner surface by a pin 94 is positioned over the boss 59 and provides a check valve preventing the return of fluid from the brake system through the perforations 65 of the cap. The cap is provided with a seat 6B having a reinforcing ring 61 therein.

The opposite end of the cylinder I3 is provided with a disc 68 which forms a head therein, the peripheral edge of the disc being held against a shoulder 59 by a spring ring 10. The disc 68 is provided with a boss 1I over which the end of the spring 50 is positioned and an opening 12 is provided through the boss and disc.

The cylinder I3 is also provided with an enlarged area 13 positioned beyond a shoulder 14 and a plurality of openings 'I5 with restricted inner ends 1S extend through the wall of the cylinder, as shown in Figure 3.

The outer end of the piston I4 is provided with a cup-shaped packing washer I1, the washer being held in an annular recess 'I8 and positioned against a flange 19 which is positioned to travel in the enlarged outer section 13 of the cylinder. A similar sealing washer 39 is provided in a recess 8l in the piston and a cup-shaped washer 82 is positioned against the end of the piston. The washer 82 is held against the end of the piston I4 by a spring 33 which also holds the piston in the position shown in Figure l, against the disc 68 in the inner end of the cylinder I3.

The brake cylinder housing I I is provided with a cover plate 84 that is held in position by bolts 85, threaded into lugs 86 in the upper end of the housing. The housing is also provided with mounting flanges 91 and 88, with bolt holes 89 and 99 therein respectively, and a drain plug 9| which may be positioned at any suitable point in the lower part of the housing.

In the design shown in Figure l2 a master cylinder 92 similar to the cylinder I9 and provided with a piston 93 is positioned in a housing 94 and a plug 95 is threaded into an opening 96 in the housing. The plug 95 is aligned with the cylinder 92 and a spring 91, similar to the spring 50, is positioned aaginst the plug and piston 93.

In this gure the check washer 98 similar to the check washer 43 is shown spaced from the inner end of the bore in the end of the piston so that a Vacuum that may result from the returning movement of the piston is broken and the pressures equalized on both sides of the piston.

With the parts arranged in this manner the improved master cylinder and booster are installed in a motor vehicle, or other device in the usual manner with the tube 51 connected to the line to the brakes, or the like and as the foot lever is pressed downwardly the rod 2B moves inwardly forcing the piston I2 through the cylinder Il) and with this movement low pressure is built up in the cylinder and also in the cylindrical casing I5 whereby the fluid is forced through the openings 'I5 and 16 into the booster cylinder I3 from where it passes through the perforations 6-5 of the cap 62 into the brake line through the tube 51. By this means the brakes are applied and with continued movement 'of the foot lever the pressure continues to build up with the fluid passing through the opening 12 into the cylinder I3 where it contacts the end with an easy movement and the movement is gradually accentuated until the high pressure fluid iinally forces the brake shoes into positive gripping relation with the drums.

With the initial movement of the foot lever the piston I2 starts to travel inwardly with the cup washer 31 closing the port 49 so that the only escape of uid in the inner end of the cylinder I0 and casing I5 is through the ports 'I6 into the cylinder I3 and from there into the brake line. Upon return movement of the piston the vacuum is relieved with the pressure thereof opening the check washer 43 whereby communication is established between the master cylinder housing II and the interior of the cylinder through the port 48.

This master cylinder and booster combination, therefore, insures positive action in both applying the brakes and also in the release thereof.

It will be understood that modifications may be made in the design and arrangement of the parts without departing from the spirit of the invention.

What is claimed is:

1. In a brake system including a master cylinder having a piston therein, a cylindrical casing, a cylindrical boss extending into said casing and provided with an annular hub, said boss having its inner end shaped to provide a booster cylinder, a nut arranged in engagement with the interior of said hub, there being an opening in said nut, a tube extending from the opening in Asaid nut and adapted to be connected to the brake system for the passage therethrough of brake uid, a perforated cap arranged contigu- 6 ous to the inner end of said nut, a resilient washer positioned adjacent the inner surface of said cap, a pin for maintaining said washer connected to said cap, a coil spring having an end engaging said cap, a piston reciprocably mounted in said cylinder, a cup shaped washer positioned against an end of said last named piston and engaging said coil spring, there being a space between said cylinder and casing, said cylinder being provided with -a plurality of spaced openings for establishing communication between said space and the interior of said cylinder, the interior of said cylinder being provided with an enlarged chamber, an annular flange extending from said last named piston and adapted to travel in said enlarged chamber, a shoulder arranged interiorly of said cylinder, a disc abutting said shoulder and provided with a central opening therein, there being a tapered finger on the end of said last named piston mounted -for movement into and out of bridging relation with respect to the opening in the disc, and resilient means interposed between the piston of the master cylinder and said disc.

2. The apparatus as described in claim 1, wherein said resilient means comprises a coil spring.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 1,885,121 Loweke Nov. 1, 1932 2,126,490 Martin Aug. 9, 1938 2,166,742 Lam-bert July 18, 1939 2,191,716 Hunt Feb. 27, 1940 2,232,113 Katcher Feb. 18, 1941 2,239,673 Fowler Apr. 29, 1941 2,272,360 Swift Feb. 10, 1942 2,273,924 Bowen Feb. 24, 1942 2,396,155 Christensen Mar. 5, 1946 2,446,884 Price Aug. 10, 1948 2,564,137 Wahlberg Aug. 14, 1951 

